1. Field of the Invention
The invention relates to a display supporting device for movably supporting a display on a body of a text processing system or the like.
2. Description of Related Art
FIG. 5 shows a text processing system having a body 5 and a display 1 that is rotatably supported on the body 5 so as to be kept in an arbitrary rotational position.
The body 5 of the text processing system is provided at its upper front portion with a keyboard 20 for inputting text, and is also provided with an insert opening and an eject opening behind the keyboard 20 for inserting and ejecting the printing paper. The body 5 is further provided at its right side portion with a display supporting device for supporting the display 1 on the body 5, whereby the display 1 is rotatably supported on the body 5 so as to be able to be moved to an arbitrary, operator selected rotational position and then fixed at that position.
The structure of a known display supporting device for a text processing system as described above will be described with reference to FIGS. 6 and 7.
FIG. 6 is a partially cutaway sectional view of the text processing system having the conventional display supporting device.
In this text processing system, a generally U-shaped frame 10 is fixed by screws to a lower cover 8, of the body 5, and an arm shaft 6 is fixed to the frame 10. A joint 2 for supporting the display 1 through an arm pipe 3 is rotatably supported on the arm shaft 6. The joint 2 is prevented from axially disengaging from the arm shaft 6 by inserting a screw 40 through the joint 2 into a circumferential groove 41 formed on the arm shaft 6.
A friction plate 13 is rotatably supported on the arm shaft 6 on the left side (as viewed in FIG. 6) of the joint 2. The friction plate 13 is formed on its right side surface with a plurality of projections 11, and the joint 2 is formed at its left end, adjacent to the right side surface of the friction plate 13, with a plurality of holes for respectively engaging the projections 11 of the friction plate 13, whereby the friction plate 13 is rotatable together with the joint 2.
An annular cork plate 12 is rotatably supported on the arm shaft 6 between the friction plate 13 and a right vertical portion of the frame 10.
A torque spring guide 17 is fixed by a screw 18 to the arm shaft 6 between the right and left vertical portions of the frame 10. A torque spring 16 is mounted on the arm shaft 6 between the torque spring guide 17 and the right vertical portion of the frame 10. The torque spring 16 is fixed at its one end to the friction plate 13 and is fixed at the other end to the torque spring guide 17. As viewed in FIG. 5, the torque spring 16 serves to normally bias the display 1 in a clockwise direction through the friction plate 13, the joint 2 and the arm pipe 3, thereby preventing the display 1 from rapidly falling down in the forward direction, that is toward the keyboard 20.
The arm shaft 6 is formed at its right end portion with external threads 14. A knob 4, having internal threads, is fastened to the external threads 14 of the arm shaft 6 so as to axially leftwardly urge the joint 2 through a washer 15.
The joint 2, the friction plate 13, the cork plate 12, the frame 10 and the torque spring 16, arranged between the torque spring guide 17 and the washer 15, are forced into a contact relationship with each other by the fastening force of the knob 4 with the force having a variable strength depending upon an extent of screw fastening of the knob 4.
Thus, the strength of the maximum frictional force generated between the contact surfaces (frictional force generating portion) of the frame 10 and the cork plate 12 and the strength of the maximum frictional force generated between the contact surfaces (frictional force generating portion) of the cork plate 12 and the friction plate 13 are dependent upon the screw fastening force applied by the knob 4.
Accordingly, when the knob 4 is loosened by a user, to decrease the fastening force, it decreases the maximum frictional force and the display 1 may be rotated relative to the body 5 to any position desired by the user. Thereafter, when the knob 4 is tightened by the user, to increase the fastening force, it increases the maximum frictional force and the display 1 is fixed at the desired position so that the user may operate the text processing system with the display 1 fixed at the desired position.
Further, in the above conventional text processing system, the display 1 is prevented from rapidly falling down in the forward direction, even in the loosened condition of the knob 4, but it is not prevented from rapidly rotating in the rearward direction.
Accordingly, when standing the text processing system on a surface 21 and the knob 4 is in a loosened condition, as shown in FIG. 7, the display 1 rapidly rotates toward the surface 21 by a rotation moment W1, caused by gravity's effect on the display 1 and the arm pipe 3, and a rotation moment T1, due to the torque spring 16. Thus, there is a possibility that the display 1 may strike against the surface 21 and be broken.